ACID SENSITIVITY AND WATER CHEMISTRY CORRELATES OF AMPHIBIAN BREEDING PONDS IN NORTHERN WISCONSIN, USA

Fifty-one amphibian breeding sites in northern Wisconsin were sampled in two surveys, in 1986 and 1987, to determine the chemical conditions and amphibian inhabitants present. All twenty-one ponds in 1986 and twenty-eight in 1987 were mildly acidic and sensitive to acidification. The pH levels encountered were generally not toxic to the resident amphibians, and may have been related to levels of phenolics in some cases. Soil type and forest canopy coverage appeared to influence the chemistry of these ponds and a direct relationship of amphibian species richness with pond size was found. Only larger ponds were long-lived enough for metamorphosis of amphibian larvae, suggesting an importance for recruitment. They were also the most sensitive ponds and the only ones to enter the chronically toxic pH range for ambystomatid salamanders, possibly placing them at risk to future acid inputs.